Grape growers should be focused on more nutrients than NPK, according to specialists within the industry.

“Grape growers should be pulling tissue samples now and continuing that through the summer,” says Chuck Moran, total nutrition system (TNS) coordinator with Wilbur-Ellis in Fresno, Calif. “Some guys like leaves. Some like petioles. We pull a combination of leaves and petioles. When you pull a petiole sample, you get pretty accurate information on nitrates and your water soluble elements.”

A leaf sample, however, is much more accurate at identifying minor nutrient levels, according to Moran.

“If you’re going to go to all the trouble to walk out in the vineyard and take samples, you might as well do both and have the advantage of getting the full spectrum of information,” he says. “It’s not really that much more expensive when you look at it on a per acre basis.”

Minor nutrients are often overlooked, but they are important in the growth and health of a vine, according to Moran.

A majority of California soils have chronic zinc deficiency, he says. There are at least another dozen minor elements that are essential to plant growth.

“If you just run an NPK sample, you’ll never pick up on a good portion of what’s missing,” Moran says.“